add environment variable to point admin sdk at rtdb emulator

[jmwski]

Hey there! So you want to contribute to a Firebase SDK?
Before you file this pull request, please read these guidelines:

Discussion

• Read the contribution guidelines (CONTRIBUTING.md).
• If this has been discussed in an issue, make sure to link to the issue here.
  If not, go file an issue about this before creating a pull request to discuss.

Testing

• Make sure all existing tests in the repository pass after your change.
• If you fixed a bug or added a feature, add a new test to cover your code.

API Changes

• At this time we cannot accept changes that affect the public API. If you'd like to help
  us make Firebase APIs better, please propose your change in an issue so that we
  can discuss it together.

[jmwski]

Abandoned and replaced by #596

[ryanpbrewster]

I think we need to re-open this PR and discuss using fake credentials for the emulators. Right now we're requiring developers to either do this themselves, or use a real production service account credential.

[schmidt-sebastian]

If I am not mistaken, the protocol is omitted in FIRESTORE_EMULATOR_HOST. I see that it might make sense to include it here (since we need to include the namespace). Should we come up with a consistent pattern that apploes to both RTDB and Firestore? @ryanpbrewster

[ryanpbrewster]

the protocol should not be included in the FIRESTORE_EMULATOR_HOST variable.

[schmidt-sebastian]

Do we care about the consistency between FIRESTORE_EMULATOR_HOST and FIREBASE_DATABASE_EMULATOR_HOST?

[ryanpbrewster]

Yes, ideally neither should include the protocol.

[jmwski]

This comment is dated, neither emulator host variable has a protocol.

[dungahk]

I totally agree with reopening this, or at least reverting #602

I am wondering how a new feature in the Firebase JS SDK is sufficient for the firebase-admin Node SDK?

For example, I am using firebase-admin with firebase-functions and I do not touch the firebase JS client SDK and having this in the admin SDK would be really appreciated.

The only weird thing I found is that if I run the emulators using emulators:start and manually invoke the functions it seems to work, but if I try to automate the steps using emulators:exec it doesn't work.

[samtstern]

@dungahk can you open a new issue on the firebase-tools repo describing the issue you're having with emulators:exec versus emulators:start?